Cast shrink on an enemy then kill it. The enemy will display its death animation twice, once for the shrunken model, then again for the full size model. After the second animation completes, the battle will not continue. It will be the turn of whoever struck the killing blow, but there will be no option to skip or go forward. Fast-forwarding doesn't work. Auto-completing the battle does, except that you get no experience for killing the shrunken unit (e.g. the summary screen will show zero exp for your heroes if there was only a single enemy in the battle).